Polymers, and in particular, polyester polymers are frequently made containing one or more additives depending upon the desired end use of the polymer. For example, in the case of polyester polymer, it is common to incorporate one or more ultra-violet inhibitors, particles for improving the reheat of bottle preforms made from the polyester polymer, toners or pigments or colored particles, acetaldehyde scavengers or inhibitors, catalyst deactivators or stabilizers, oxygen barrier material, friction reducing aids, crystallization aids, impact modifiers, and so forth. In some cases, these additives are insoluble in the polymer and require good mixing. Additionally, some additives may be sensitive to exposure to high temperatures for extended periods of time as typically seen in a polycondensation process. In other cases, some additives may inhibit the activity of catalysts.
Thus, there is a desire to provide a method for adding the additives to a polymer melt stream in a manner which at least minimizes exposure time to high temperatures, or does not inhibit activity of catalysts, or provides for good mixing, or a combination of the foregoing.
Methods for adding additive dispersions or solutions in low molecular weight carriers such as ethylene glycol, or in higher molecular weight reactive carriers such as polyoxyalkylene polyols, into a melt phase reaction after esterification and into polycondensation are also known. These processes, however, result in adding extra glycol into an oligomer mixture or into the polymer melt, which is undesirable in some cases especially as one proceeds further toward concluding the polycondensation reaction. Adding the additive neat without a carrier is usually too difficult to meter or add in desired amount.